1. Field of the Invention
This invention relates generally to the transdermal electrokinetic mass transfer of medication into a diseased tissue, and, more specifically, to a medicament containing iontophoresis electrode for the delivery of medication across the skin and into diseased tissues and blood vessels adjacent to the delivery site.
2. Prior Art
Iontophoresis has been employed for several centuries as a means for applying medication locally through a patient's skin and for delivering medicaments to the eyes and ears. The application of an electric field to the skin is known to greatly enhance the skin's permeability to various ionic agents. This permeability change has been used, for example, to enhance transcutaneous transport of glucose for monitoring blood glucose levels. The use of iontophoretic transdermal delivery techniques has obviated the need for hypodermic injection for many medicaments, thereby eliminating the concomitant problems of trauma, pain and risk of infection to the patient.
Iontophoresis involves the application of an electromotive force to drive or repel oppositely charged ions through the dermal layers into a target tissue. Particularly suitable target tissue include tissues adjacent to the delivery site for localized treatment or tissues remote therefrom in which case the medicament enters into the circulatory system and is transported to a tissue by the blood. Positively charged ions are driven into the skin at an anode while negatively charged ions are driven into the skin at a cathode. Studies have shown increased skin penetration of drugs at anodic or cathodic electrodes regardless of the predominant molecular ionic charge on the drug. This effect is mediated by polarization and osmotic effects.
Regardless of the charge of the medicament to be administered, a iontophoretic delivery device employs two electrodes (an anode and a cathode) in conjunction with the patient's skin to form a closed circuit between one of the electrodes (referred to herein alternatively as a "working" or "application" or "applicator" electrode) which is positioned at the delivered site of drug delivery and a passive or "grounding" electrode affixed to a second site on the skin to enhance the rate of penetration of the medicament into the skin adjacent to the applicator electrode.
Recent interest in the use of iontophoresis for the transdermal delivery of drugs to a desired cutaneous or subcutaneous treatment site has stimulated a redesign of many of such drugs with concomitant increased efficacy of the drugs when delivered transdermally. As iontophoretic delivery of medicaments become more widely used, the opportunity for a consumer/patient to iontophoretically self-administer a transdermal dosage of medicaments simply and safely at non-medical or non-professional facilities would be desirable and practical. Similarly, when a consumer/patient travels, it would be desirable to have a personal, easily transportable apparatus available which is operable for the iontophoretic transdermal delivery of a medication packaged in a single dosage applicator. A problem which presents an impediment to potential users is the necessity for reformulating medicaments for iontophoretic delivery. Such reformulations must be approved by cognizant regulatory agencies prior to sale. This requires delay and additional expense for the manufacturer, which additional expense may be passed along to consumers. The present invention provides a disposable medicament dispensing electrode for use with a portable iontophoretic medicament delivery apparatus in which the electrode is adapted for use with the apparatus for self-administering medicament. The medicament dispensing portion of the electrode can accept, store and dispense presently approved medicament formulations.